Rotation of the stylet bundle in the southern green stink bug, Nezara viridula (L.)

Authors: Esquivel, Jesus; Droleskey, Robert - Bob; Harvey, Roger

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2021
Publication Date: 12/17/2021
Citation: Esquivel, J.F., Droleskey, R.E., Harvey, R.B. 2021. Rotation of the stylet bundle in the southern green stink bug, Nezara viridula (L.). Southwestern Entomologist. 46(4):867-878. https://doi.org/10.3958/059.046.0408.
DOI: https://doi.org/10.3958/059.046.0408

Interpretive Summary: The southern green stink bug uses needle-like mouth parts known as stylets to transmit plant pathogens and to feed on various plant structures. The mouth part is composed of an outer pair of stylets which encompasses an inner pair of stylets to form the feeding apparatus. Although the surface characteristics of the stylets are known, the orientation of the feeding apparatus has not been previously described. We cut the feeding apparatus into cross-sections and obtained high resolution images of each section using a light and transmission electron microscope. The images revealed a counterclockwise rotation to the feeding apparatus along the entire length of the mouth part. This work improves our understanding on the orientation of the stink bug needle-like feeding apparatus and, more importantly, provides additional insight on its relationship with the insect’s internal anatomy, feeding behavior, and pathogen transmission.

Technical Abstract: The southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), uses a needle-like stylet bundle to feed on cotton (Gossypium hirsutum L.) bolls and other high-value crops, occasionally introducing disease-causing pathogens to developing fruit. Ongoing efforts to better understand the role of the stink bug stylets in pathogen transmission potential yielded the first evidence of a rotational aspect to the stylet bundle of the southern green stink bug. Our objective is to provide the first imagery and descriptions of the observed rotation of the southern green stink bug stylet bundle. From the point of origin, a counterclockwise rotation occurs along the length of the stylet bundle in the southern green stink bug. A 90° counterclockwise rotation is observed within a span of approximately 195 µm of the stylet bundle in the insect head as the stylet bundle enters the labrum, and the rotation continues into the distal labial segments. Distally, the interlinkage between the maxillary and mandibular stylets is reduced enabling the maxillary stylets to operate independently and possess their own rotation aspect. This report confirms and describes the stylet bundle rotation within the southern green stink bug. Moreover, we add to the knowledge base in describing the degree of rotation and the existence of a separate rotation aspect to the maxillary stylets distally. Additional work may be warranted to determine the degree of rotation in other phytophagous stink bugs and to correlate the likelihood of pathogen transmission based on stylet bundle rotation potentially affecting feeding behavior.